Bioprecipitation Of Phosphorus And Cadmium By Marine Bacterium Pseudoalteromonas Sp. DSBS

Modem human activities broke the phosphorus circulation in ecosystem and accelerate the one-way flow of phosphorus, causing eutrophication. The available phosphorus resources are exhausted, forming the global crisis of phosphorus. These make the research on recycling of phosphorus resource by phosphorus precipitation be taken more and more seriously. The process and the mechanism of widespread phosphorus precipitation in nature have been not clear, seriously limit phosphorus removal rate and the recovery rate of phosphorus in wastewater treatment. The correlation of phosphorus and cadmium in ocean and phosphate rock suggest that there may exist a certain inner link between the detoxification of cadmium in microorganisms and the precipitation process of phosphorus. Therefore, this paper used the bacteria Pseudoalteromonas sp. DSBS (P. sp. DSBS) with highly cadmium removal ability which was found in the previous research of our group to study the removal and precipitation process of phosphorus and cadmium in synthetic wastewater medium. The research develops the related theoretical basis of aerobic bio-metal-phosphate precipitation, and provides theoretical guidance for the bio-phosphorus removal and phosphorus recycling. The main results and conclusions are as follows:First, the measurement of dynamic change of supernatant phosphorus and cadmium concentrations and the accumulation of phosphorus and cadmium in different positions of bacteria during the removal of phosphorus and cadmium was performed. Statistics analysis, correlation and interaction were analyzed. The migration rules of phosphorus and cadmium under the action of bacteria was cleared. The study found that in the medium, the bacteria could remove 95.74% of 9 mg/L phosphorus in 8 h, and 97.53% of 8 mg/L cadmium in 36 h. But cadmium of biological phosphorus removal is not synchronous. In 0-3 h, bacteria rapidly absorbed phosphorous. H+ released by bacteria produced competitive adsorption with Cd(Ⅱ) cations. In 4-8 h, bacteria secreted more extracellular polymeric substances (EPS) and alkali substances. Cadmium began to be removed. After 8 h, phosphorus and cadmium in EPS was precipitated extracellularly at the molar ratio of 1.50-1.65, which removed phosphorus and cadmium and detoxified cadmium.5 mg/L phosphorus were enough to detoxify 8 mg/L cadmium.AFM, SEM, XPS,31 p NMR, Visual MINTEQ software prediction, desorption agent desorption and other modern instrumental analysis technologies and experimental designs were used to characterize and analyze the generated precipitation. Research has shown that alkali substances changed the species of cadmium and reduced its toxicity. Alone and grape clusters forms of nanoparticles, which were consisted of cadmium-phosphorus-sulfide and polysaccharide and 25-60 nm in diameter, generated at the surface of bacteria. Cd(II) combined with O of PO4 in EPS, and 32.89% of phosphorus in EPS were organic.The study of other common forms of phosphorus in the environment source showed that compared with the inorganic phosphorus source, strain P. sp. DSBS had efficient hydrolysis ability for organophosphate and polyphosphates, and the same efficient phosphorus and cadmium removal performance. Glycerin sodium phosphate as the phosphorus source, more phosphorus and cadmium accumulated in EPS, and bacterium showed higher ability of precipitation.Based on the above research results, the biochemical mechanism model about the co-removal and precipitation process of phosphorus and cadmium by P. sp. DSBS was preliminary established. Phosphorus, EPS and extracellular alkaline substances produced by bacteria played an important role in the process of cadmium removal and precipitation. Organic phosphate metal nano precipitated was formed in EPS with specific stoichiometric ratio of phosphorus and cadmium for detoxification. This process may provide a new explanation for the biological phosphorus-metal deposition process in geochemical cycle.